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Mug Failures
Done quite a few mugs over the weekend and had a few failures on both the 11oz RN coated mugs and on frosted glass. I have turned the standby temperature on the press down to 90 degrees and will probably go a little lower. If Im doing a large run I pre-heat the mugs to about 50 degrees in the oven , but still get cracking. The ceramics seem to get subtle cracking on the glaze and catastrophic cracking on the glass.
What do you consider an acceptable failure rate (I know zero is ideal) if doing a batch of 50. Is 3 out of 25 (or 12%) bad????
Views on this greatly appreciated.
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31 Replies
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If you are talking about faulty mugs rather than faulty prints I wouldn’t expect any. You shouldn’t be having cracking on either item as they are meant for this purpose. If your temps and times are correct then this shouldn’t be happening. We print thousands every month and don’t get cracking at all, just perhaps the odd faulty print for various reasons. Temp we use is currently 195c and they go in the presses cold. No dipping after. Had a handle fall off a glitter mug a few days ago but that is the last faulty mug I can remember.
What temps/times/process do you use?
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Mugs going in at either room temp or for glass preheated. Press set to a medium/low pressure 180 degrees for 3 minutes. Press is currently set to 90 degrees for standby…………Im not using cheap mugs either!!!
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For ceramic mugs we press at 195 for 2min 10sec and find this ideal. This is in the NC double head presses. Room temp which is quite cold in our warehouse and been the same throughout winter. Never get any cracking. I understand the glass mugs will be slightly more delicate but to have faults with both shouldn’t be the case. From the settings you state these problems shouldn’t be happening. Is the cracking happening all over or in a constant place?
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190 for 2.30 here, then drop into warm water to cool.
out of 50 mugs I would be looking for 50 🙂
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quote Neil Speirs::lol1: out of 50 mugs I would be looking for 50 🙂Why don’t you just say "You’re crap a printing mugs Graeme"
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quote Dave n Rob Lowery:quote Neil Speirs::lol1: out of 50 mugs I would be looking for 50 🙂
Why don’t you just say “You’re crap a printing mugs Graeme”
OK…….got me 🙂
Not had a single problem with the print quality, just not keeping all of the mugs. Even had one that went to the customer that leaked through a hairline crack in the base!!! Left an embarrassing wet patch on his trousers….lucky for me he had a sense of humour and ordered more!!!
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quote Dave n Rob Lowery:quote Neil Speirs::lol1: out of 50 mugs I would be looking for 50 🙂
Why don’t you just say “You’re crap a printing mugs Graeme”
:doh: I knew I forgot something
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are u dropping them in cold water to cool em?
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quote Neil Speirs:are u dropping them in cold water to cool em?
I wish, not getting that far, all 3 glass mugs shattered in the press and the ceramics cool naturally. When they are heating in the press you get the usual quiet "tings" during heating, but sometimes a slightly louder noise, and I know the glaze has cracked, usually inside the mug. Not normally noticed on a new mug, but after a few cups of tea/coffee the light crazed lines appear stained.
Oh and thanks for all the POSITIVE and SUPPORTIVE comments :lol1:
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Graeme – I had a problem whereby the images were scorching. Turns out the temperature settings on my press were way out. After advice from Martin I dropped the idle temp to 90 and the cooking temp to 150. The mug goes in at 90 and the 3 minutes baking time doesn’t start until it hits 150. Perfect results following this tweak.
Maybe give that a try and see what happens.
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I print all my mugs at 200 degrees for 210 seconds this is with no preheating, the press warms them up to the correct temp as it reaches 180 seconds IE the 3 mins we would press for, in a batch of 1000 I would expect no failures, if at all just on the print if the tape slipped etc but certainly no cracking or damage.
The only time I have had rejects is where the tape had slipped due to carelessness and the image ghosted as the mug came out of the press. -
quote Graeme Harrold:quote Neil Speirs:are u dropping them in cold water to cool em?I wish, not getting that far, all 3 glass mugs shattered in the press and the ceramics cool naturally. When they are heating in the press you get the usual quiet “tings” during heating, but sometimes a slightly louder noise, and I know the glaze has cracked, usually inside the mug. Not normally noticed on a new mug, but after a few cups of tea/coffee the light crazed lines appear stained.
Oh and thanks for all the POSITIVE and SUPPORTIVE comments :lol1:
This is probably a really stoopid thought, but is the pressure on the press too high? Just that as no-one else seems to have had this problem, and it happens on both types of item Graeme….
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Where are the mugs from?
Have you tried making a mug from cold without the pre heating? see if it still happens.
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I also use medium high pressure too.
:lol1: -
quote Steve Underhill:I also use medium high pressure too.
:lol1:Well I did say it was a daft idea, but the pressure applied isn’t exactly ‘scientific’, and what appears to be easily clamped by one person may be very difficult to close for another. Sorry. 😥
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Oh! Sod It…..time to sub-contract Graeme 🙄
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quote Lorraine Clinch:quote Steve Underhill:I also use medium high pressure too.
:lol1:Well I did say it was a daft idea, but the pressure applied isn’t exactly ‘scientific’, and what appears to be easily clamped by one person may be very difficult to close for another. Sorry. 😥
No Loraine what I meant was I forgot to add that in my reply, it wasnt a daft idea. . 🙂
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quote Dave n Rob Lowery:Oh! Sod It…..time to sub-contract Graeme 🙄
Would have expected that comment from Steve 😀
Got another batch of mugs arriving from another supplier and see ho that goes. Will also double check the actual temp of the press, thanks Mark.
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quote Neil Speirs:Where are the mugs from?
Have you tried making a mug from cold without the pre heating? see if it still happens.
Done this from the start, sometimes quite cold and it takes a while to get up to temperature. Problem I find if they are too cold is the print along the base can seem faded due to the additional heat (quantity) required for the base.
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Sorry u may have said already but is it a press or oven your using Graeme?
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quote Neil Speirs:Sorry u may have said already but is it a press or oven your using Graeme?
Definitely a press…………..
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it sounds like it’s gotta be the mugs then……u sure they ain’t from ebay 🙄
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Definitely all from a reputable supplier who is currently asking questions of his suppliers. Mugs are RN coated so not rock bottom.
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Graeme – have you got any other mugs to try? I am in Swansea if you want to nick some of mine or even try yours in one of my presses.
The thing that confuses things a little more is that you are also having problems with the glass mugs otherwise I would say it would be clear cut that you have a dodgy batch of ceramic mugs.
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I know glass is a strange material. Technically a liquid at all temperatures, it has a crack failure of about 0.05mm i.e. its structural integrity is severely compromised. Certainly gives me plenty to go back with.
My plan now is to double check the actual temperature the press reaches (does have a digital read out)
Try a different mug, having said this Ive done 15oz with no problems 😕This will have to wait till Thursday when I am reunited with my equipment
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quote ADW:Graeme – have you got any other mugs to try? I am in Swansea if you want to nick some of mine or even try yours in one of my presses.
The thing that confuses things a little more is that you are also having problems with the glass mugs otherwise I would say it would be clear cut that you have a dodgy batch of ceramic mugs.
Thanks for the offer, but Im at the other end of the country….. :lol1:
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quote Graeme Harrold:This will have to wait till Thursday when I am reunited with my equipment
Sounds painful! 😮
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Defo sounds like mug failure and nothing to do with equipment. You would have to put alot of pressure on the press to crack a mug. I have seen mugs pressed to oval in the press and come out perfect. I never have had a fail due to breaking in the press.
Had a lot arrive broken mind. 😀 😀 😀 😀Peter
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I know I still have them Pete :lol1:
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Just posted some of the successful mugs here
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Ive done a few hundred mugs over the months, and never had one failure. Now by reading all of these posts I am now wondering if i am just lucky. I pull a box of mugs from the shed, stick the print to them blast them at 200 for 2 mins then dunk them in cold water, never once had one crack, so I think I will try this weeks lottery.
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